Additional Chief Metropolitan Magistrate Samar Vishal also acquitted Deputy Chief Minister Manish Sisodia, a co-accused with Kejriwal in the defamation case lodged by Sibal, after he too tendered an apology to the lawyer through a letter.
The relief came from the court after the apologies were accepted by the complainants in both the cases.
The proceedings against lawyer Prashant Bhushan and BJP leader Shazia Ilmi will, however, continue in the defamation case lodged by Amit Sibal.
Kejriwal, in his two separate apology letters, said he regretted making the remarks without any verification and accepted that they were based on "unfounded allegations".
In the 2013 case lodged by Amit Sibal it was alleged that Kejriwal, Sisodia, Bhushan and Ilmi, who was then an AAP member, had targeted him and his father Kapil Sibal over the Vodafone tax revision case.
In the defamation case filed by Gadkari, it was alleged that Kejriwal had called him "India's most corrupt".